Use of thyroid stimulating hormone testing in newborns to identify iodine deficiency.

Iodine deficiency has traditionally been associated with goiter and cretinism. More recently, iodine deficiency has been recognized as the leading worldwide cause of preventable intellectual impairment. Intellectual and neurologic deficits occur because of a lack of thyroid hormone during critical phases of brain development. More sensitive biologic tests may be useful in determining the true extent of iodine deficiency in populations. Thyroid stimulating hormone (TSH) levels among urban newborns from countries with known iodine deficiency problems were determined using a sensitive whole-blood spot assay. Results found prevalences of high TSH (> 5 mU/L whole blood units using a sensitive monoclonal assay) ranging from 32-80% compared with a prevalence of 3% usually found in iodine-replete areas. These findings suggest that developing brains of newborns are at risk from the detrimental effects of iodine deficiency in these urban areas. The results presented suggest the need for effective intervention programs in urban areas as well.